Olympic chiefs should not use women's sport as a "live experiment" on the issue of transgender athletes, ex-swimmer Sharron Davies has warned.
The British Olympic silver medallist has been vocal on the subject in the past and wants the International Olympic Committee to "show leadership".
She spoke out as the IOC said it was assessing its guidelines in time for the 2020 Summer Olympics in Tokyo.
"If there is any doubt, delay inclusion," Davies said.
Davies, who won silver at the Moscow Games in 1980, added: "Do not use women's sport as a live experiment. That's not right or fair."
She believes people born biologically male who transition after puberty will retain a physical advantage over their competitors, and that their participation should be limited until the science is clear on the issue.
Trans athletes have argued they should not be blocked from participating in sport, and some have claimed the science around physical benefits is still unclear.
Davies, along with Dame Kelly Holmes, double gold medal winner at the 2004 Olympics, and marathon world record holder Paula Radcliffe, with the support of 60 other top-class athletes, wrote to IOC president Thomas Bach in March this year urging him to further investigate this issue.
The current IOC guidelines, issued in November 2015, state that transgender women must suppress testosterone levels for at least 12 months before competition. Testosterone is a hormone that increases muscle mass.
Athletes transitioning from female to male are allowed to participate without restrictions.
The governing body of Olympic sports says it is trying to strike the right balance between fair and equal competition and non-discrimination.
"The IOC is still working to develop new guidance to help international federations shape sport-specific policies and regulations in relation to fairness, safety, inclusivity and non-discrimination," it said.
"Our approach to providing guidance on participation is based on an ever-evolving area of research and learning."
The IOC added its finished guidelines would be "subject to periodic review".
At the Pacific Games in Samoa in April, transgender competitor Laurel Hubbard won two gold medals in weightlifting in the +87kg category. The New Zealand athlete, 41, had been favourite to win the gold at the Commonwealth Games in Australia last year but she pulled out midway through the competition on the Gold Coast with an elbow injury.
As things stand, Hubbard would be eligible to compete in Tokyo and could become the first transgender athlete to win an Olympic medal.